EEG sleep patterns as a function of normal and pathological aging in man

Sleep and human cerebellar pathology

The organization and the quantitative evaluation of sleep stages were studied in patients with cerebellar syndrome. 25 polygraphic night recordings were scored according to the criteria suggested by Rechtschaffen & Kales (1968) and the sleep parameters investigated were referred to those indicated by Williams et al. (1974). The results matched with a homogeneous sample of normal subjects. Significant alterations were observed for several parameters of sleep, and the possible causes discussed.

Sleep disturbances in a series of elderly patients: polysomnographic findings

A group of 27 elderly patients with complaints of either chronic insomnia or excessive daytime sleepiness were studied in the Sleep Evaluation Center of Western Psychiatric Institute and Clinic during the period January 1977-June 1979. On the basis of anamnestic data from patients and bedroom partners, together with polysomnographic findings, sleep disturbances were classified according to the nosology of the Association of Sleep Disorders Centers. Of the 27 patients, 19 had disorders of initiating or maintaining sleep (DIMS), 7 had disorders of excessive somnolence (DOES), and 1 had parasomnia (episodic nocturnal wandering). Of the 19 DIMS patients, two-thirds had either a primary affective disorder (depression) or a persistent psychophysiologic disturbance. Of the 7 DOES patients, 6 had a primary sleep disorder such as a sleep apnea syndrome or narcolepsy-cataplexy. Additional electroencephalographic sleep data are presented on elderly patients with primary nonpsychotic depression. The latency of rapid eye movements (REM) in the depressed patients was shorter (p less than 0.05) than in patients with a persistent psychophysiologic disturbance. The percentage of REM sleep was significantly elevated (p less than 0.05) in the depressed group, and intermittent wakefulness was decreased (p less than 0.01). The causes of sleep disturbance in the elderly are both heterogeneous and complex. The need for accurate differential diagnosis and a multiaxial approach is stressed.

Time-related changes in the distribution of sleep stages in brain injured patients

The correlation between sleep pattern and cognition was studied in a follow-up of 9 patients with traumatic brain injury. The follow-up extended for a mean of 38 weeks after regaining consciousness, with 4-7 study periods for each patient. In addition to sleep pattern, 3 other variables were evaluated: independence in activities of daily living, locomotor and cognitive functions. In 7 patients there was a high correlation (r greater than 0.89) between cognition and REM sleep improvement whereas in 2 patients the correlation was lower (r less than 0.6). It is suggested that in the first group the REM mechanism was intact whereas in the latter, where a brain stem lesion was present, the REM mechanism was damaged. It is also suggested that the sleep pattern recovery time constant depends on the insult to the sleep mechanism structure whereas the REM steady-state recovery process depends on both cognitive maximal capacity and REM neural mechanism integrity.

REM ocular activity in Parkinsonian patients chronically treated with levodopa

REM ocular activity of levodopa treated Parkinsonian patients was compared to REM ocular activity of normal young adults. REM densities were significantly higher in patients than in normal controls. This difference was most prominent after 10 min of REM sleep. Previous findings that levodopa treated patients reported usually vivid and detailed dreams suggest that increase in REM ocular activity is underlying the new dreaming experiences.

Reported sleep: needed minus obtained sleep, family resemblance, and age

For a normal population from 13 to 89 yr. of age there was a correlation of .02 between age and sleep obtained, -.07 between age and sleep needed, and -.33 (p less than .01) between age and sleep needed minus sleep obtained. Also, significant family resemblance was found for all three of the above sleep variables.

An optical scan system for encoding and tabulation of visually scored sleep data

A system for computer-assisted encoding, tabulation and analysis of visually scored sleep data is presented. The main features of the system are: (1) The use of computer-readable optical scan sheets for direct encoding of the sleep data. This eliminates the need for a separate transcription and/or key-punching operation. (2) The development of a visually scored data base, organized by NREM and REM periods, which contains all items of visually scored data indexed by time and/or page of occurrence in the sleep record. The advantages of this new system are: (a) the low cost per night of operation; (b) the facilitation of analysis of cycle phenomena and testing of new hypotheses that would usually involve retabulation of the data; and (c) the facilitation of analysis of real-time correlates of visually scored sleep stages.

Are Hypnotics Helpful or Harmful to Elderly Patients?

Hypnotics are taken by a fifth of adults at home, and by half those in hospital for more than 17 days. Such prescription may be inappropriate in the elderly since their insomnia frequently results from conditions such as depression, boredom and loneliness. Furthermore the elderly are more susceptible to adverse drug reactions due to decreased efficiency in eliminating drugs from the body and increased target organ response. They are also less able to compensate for unwanted effects, which may last up to 36 hours after a single dose. Despite this, there appears little attempt to reduce dosage in old patients or to select hypnotics less likely to produce side effects. We would suggest that these drugs should be prescribed with caution in the elderly, and only after a full history and examination of the patient. The drug, dosage and length of treatment should then be selected individually.

Evoked K-complexes and cardiovascular responses to spindle-synchronous and spindle-asynchronous stimulus clicks during NREM sleep

The hypothesis that the functional role of the sleep spindle is to preserve sleep by inhibiting sensory input (Yamadori 1971) was examined. Series of 44 dB, 10 msec, 1000 c/sec 'clicks' were presented to 12 subjects at a 30-sec ISI during stage 2 sleep either during spindle bursts (i.e. spindle-synchronous clicks) or during interburst periods (i.e. spindle-asynchronous clicks). Contrary to the spindle inhibitory hypothesis, cortical EEG and cardiovascular responses showed no evidence of spindle 'suppression'. Evoked K-complexes were potentiated by the spindle-synchronous stimulation. A second study with 7 subjects replicated this result and extended the finding to include stage 3--4 sleep. It was suggested that the potentiation of evoked K-complexes was due to phasic reductions in inhibitory action during sleep spindles resulting in increased transmission of sensory events or, perhaps, an increase in the lability of certain EEG response systems.

Impaired synaptic potentiation processes in the hippocampus of aged, memory-deficient rats

A series of neurophysiological experiments was performed on the Schaffercommissural system of the hippocampus of aged and young anesthetized Fischer rats. The aged Fisher rats were previously found to exhibit retention performance deficits. No obvious differences were found between aged and young animals in amplitude, latency, stimulation threshold, or wave forms of typical synaptic responses when these were elicited by control (0.3 Hz) stimulation pulses. Further, the temporal curves of facilitation during a paired-pulse series were not different in aged and young animals. However, aged and young synapses showed consistently different responses during repetitive stimulation. Synapses of aged animals were deficient in frequency potentiation processes during 12 Hz stimulation; and the aged animals exhibited a delayed rise of post-tetanic synaptic potentiation following a 5 sec, 100 Hz stimulation train. Moreover, aged synapses 'exhausted' more rapidly during continuous 4 Hz stimulation. Throughout these studies a biphasic pattern of potentiation was observed during repetitive stimulation (brief potentiation, depression, renewed potentiation). Aged animals were deficient primarily in development of the second phase of potentiation. This pattern suggests an age-related impairment of some secondary process of potentiation, leading to an increased tendency to synaptic depression during and after stimulation. The possibility that the impaired hippocampal synaptic plasticity may be related to reported deficient behavioral plasticity in the aged animals is considered.

Does the brain actively maintain itself?

All living systems have special mechanisms for combatting entropy; however, the brain has dimensions of organized complexity beyong those manifest in the anatomical structure and physiology of the rest of the body. Reasons are given in support of the notion that the brain therefore must have a special, intrinsic "homeostatic" system for its information bearing structures, and, further, that slow electroencephalographic activity has properties which might make it useful for such an order-maintaining function. Recovery from brain damage is hypothesized to be a byproduct of this process, which may involve a cruder sort of information processing than occurs with such functions as perception and learning. Synchronized EEG activity may be adequate to handle this sort of information processing. Speculations are offered about possible mechanics, on the neuronal level, of slow wave participation in plasticity; for example, one such suggestion is based on findings that electrical fields can influence cellular orientation. The methodology of discovering the distribution within the brain of the hypothetical maintenance system is discussed briefly.

Flurazepam effects on slow-wave sleep: stage 4 suppressed but number of delta waves constant

Repeated administration of flurazepam reduced stage 4 sleep (high delta-wave concentration) but produced a greater increase in stage 2 duration so that total sleep time was increased. Computer analysis revealed that the increased amount of stage 2 (low delta-wave concentration) sleep provided a number and duration of delta waves sufficient to offset the loss of delta activity in stage 4. However, the amplitude of the average delta wave was reduced. These results demonstrate the value of direct quantification of delta-wave activity, the variable that underlies visual classification of slow-wave sleep into stages 2 to 4. They also give rise to new hypotheses regarding the relative absence of side effects in spite of profound stage 4 suppression by flurazepam and the mechanisms by which total sleep time is increased by this drug.

Ontogeny of delta activity during human sleep

The study describes the ontogenetic and time-related changes in peak amplitude, frequency, and incidence of delta waves of twenty-five normal subjects between the ages of 3 and 79 years of age. All slow waves greater then 5 muV in magnitude and between 0.5 and 3.0 c/sec were analyzed for the first 6 h of the night's sleep. In this study increasing age was accompanied by decreases in average peak amplitude of delta waves over 5 muV, slowing of delta frequencies, and decreases in incidence of waves greater than 20 muV. Across 2-h epochs of the night there were tendencies for the average peak amplitude of delta waves to decrease, for the average frequency for a given amplitude range to decrease, and for the incidence of low-amplitude delta waves to increase and high-amplitude waves to decrease. The incidence of waves greater than 5 muV remained constant across ages and epochs. Frontal channel delta waves exhibited an age-group difference whereas no such difference was apparent for central channel delta activity, suggesting that the frontal channel may possess advantages over the central because of greater sensitivity to age related changes.

The electroencephalogram in the middle-aged and the elderly

A survey was made of the electroencephalographic (EEG) changes during the human lifespan. It was found that the EEG changes during childhood and adolescent maturation continue even between the ages of 30 and 60 years. There is a decrease in the abundance of alpha activity, with a reduction in the fast part and a relative increase in the slow part of the alpha band. In the span of life between 60 and 90, there is an increase of slow waves with a progressive slowing during the aging process and a shift in the dominant frequency from 9 cps to 7 cps. Computerization of results in the beta band (above 13 cps) enables differentiation of the waves of the lower part (13-25 cps) from those of the upper part (above 25-30 cps). The lower part of the beta band decreases parallel to the alpha activity but the upper part of the beta band increases in amount during the aging process. The meaning of the divergent behavior of these sub-groups of beta activity in the aged is discussed. The EEG seems to be an important factor in the study of aged persons.

Sleep satiation in narcoleptic patients

Polygraphic sleep recording was performed in 20 narcoleptics with one or more of the auxiliary symptoms, 4 narcoleptics with only sleep attacks and 10 normals during one night and into the following day. Total sleep time in the narcoleptics did not differ significantly from that in the normals. Sleep of the narcoleptics with auxiliary symptoms was unstable with frequent awakening. The temporal organization of the REM--NREM sleep cycle was irregular in the narcoleptics with auxiliary symptoms, compared with those in the other two groups. Percentage of Stage 1 was significantly larger in the narcoleptics with auxiliary symptoms than in the other two groups and percentage of Stage 2 was smaller. Percentage of Stage 4 was smaller in the narcoleptics with auxiliary symptoms than in those with only sleep attacks. Percentages of Stages 3 and REM did not differentiate the three groups. Spindle density during Stage 2 did not differentiate the three groups. Sleep onset Stage REM was frequently observed exclusively in the narcoleptics with auxiliary symptoms. Excluding the instances showing sleep onset Stage REM, mean latency of initial episodes of REM sleep in the three groups was shorter after daytime sleep onset than after nighttime sleep onset. In the narcoleptics with auxiliary symptoms, no significant correlation was found between the percentage of Stage REM and clinical findings.

CONCLUSIONS

the sleep attacks in narcoleptics are due to an ill-timed, strong tendency to fall asleep (including both REM and NREM sleep), and it is therefore suggested that they are manifestations of their disturbed circadian rhythm of sleep--wakefulness cycle.

Effect of flurazepam on sleep spindles and K-complexes

In this research, a quantitative study of the EEG from 5 subjects permitted a detailed analysis of the effect of 30 mg of flurazepam administered over 7 nights. Four placebo baseline nights and 3 placebo withdrawal nights were also recorded. For 4 of the subjects, a nondrug and nonplacebo follow-up record was obtained 4 to 6 weeks later. The subjects were 4 females, 1 male, age range 23-42. All complained of either sleep onset greater than 45 min, sleep length of less than 6 h, or two or more sleep awakenings. Compressed spectral analysis yielded a computer-generated somnogram on each of the 15 nights of sleep, and an automated spindle detector was used to count and measure the duration of spindle bursts with frequencies of 12.25-15.5 c/sec on baseline nights 3 and 4, drug nights 1, 2, 3 and 7, on the 3rd withdrawal night, and on the 4-6 week followup record. K-complexes were scored visually on the 4th baseline and 7th drug nights. There were no significant differences in spindle rate per minute among baseline nights and the follow-up record. By the 2nd drug night, spindle rate had significantly increased over the baseline rate. Linear contrast analysis indicated there was a significant increase of spindle rate over drug nights. All 5 subjects showed this pattern of increase. In contrast to the increase in spindle activity, the rate per minute of K-complexes significantly decreased during drug administration.

The number and duration of the episodes of the various EEG stages of sleep in young and older people

Episodes of any one electrophysiological sleep stage and of intervening wakefulness were examined as to their numbers and durations in sleep of ten young normal subjects (mean age 22) and in significantly more disturbed sleep of fourteen late middle age normal people (mean age 55). No significant difference between the two age groups was found for any of the stages in the mean number of episodes taken from 4 nights. For any of the stages, the individual numbers of episodes accumulated over the 4 nights varied in a wide range and showed significant consistency with similar data obtained in another set of 4 nights. There were significant differences between the two age groups in episode duration. The sleep of the older group contained significantly higher proportions of longer episodes of wakefulness and drowsiness and significantly lower proportions of longer episodes of slow wave sleep and REM sleep. Thus, the initiation of episodes of EEG stages was on average similar in the better sleep of young and impaired sleep of older subjects, but the maintaining or termination of the episodes were different.

Some methodological problems in age comparisons of EEG sleep patterns for C57BL/6J mice

Some methodological problems encountered in age comparisons of EEG patterns are discussed in the context of an analysis of open field activity scores before and after preparation for, and recording of EEG sleep patterns. Plasma corticosterone levels 11 days after surgery for EEG electrode implantation were also measured. Activity levels were modified more for three older than for a younger group of animals following surgery/recording sessions. Corticosterone levels were appreciably elevated for the oldest group of animals. The possibility was raised that procedures designed to allow recovery from post surgical shock and adaptation to electrode connections may result in disproportionate differences across age groups.

Changes in frequency and amplitude of delta activity during sleep

Modified period analysis was applied to all-night sleep recordings from 14 young adult males. The modifications involved addition of measures of integrated amplitude and of time in frequency band to the zero crossings and zero counts of the first derivative. The analysis was directed toward changes in the characteristics of delta activity (0--3 c/sec) across the night. Delta shifted toward lower frequencies and decreased in amplitude as sleep progressed. These trends were apparent in mean values for successive periods of slow-wave sleep (SSWPs). For epochs of record classified as stage 4 EEG, these trends were seen both within and across SSWPs. The physiological significance of these changes is unknown. We suggest that they may reflect the kinetics of the metabolic processes underlying sleep. Whatever their theoretical significance, the present results provide new, normative features of the sleep EEG which are not evident in sleep stage classification. The trends we observed appear sufficiently reliable to merit empirical investigation as a function of age, clinical state, or the administration of drugs in addition to further studies aimed at determining their biological significance.

Two types of insomnia: too much waking or not enough sleep

The stability of sleep was examined in two kinds of induced insomnia, namely after caffeine administration and after hypnotic drug withdrawal. The duration of each episode of any one sleep stage or any episode of intervening wakefulness plus drowsiness was determined. After caffeine there was an increase in longer episodes of intervening wakefulness plus drowsiness, but no significant change in the episode duration of any of the sleep stages. In the case of drug withdrawal there was no change in the episode duration of intervening wakefulness plus drowsiness, but there was a significant shortening of episode duration in sleep stages 2 and 3+4, with a similar trend for REM sleep episodes. Caffeine 'insomnia' thus seems characterized by increased stability of wakefulness, and hypnotic withdrawal 'insomnia' by decreased stability fo sleep. The type of analysis undertaken in this study could increase understanding of other types of insomnia.

Absence of REM rebound after barbiturate withdrawal

Administration of three different barbiturates reduced rapid eye movement (REM) sleep. Drug withdrawal led to a return to baseline REM] values without significant overshoot. Similar results are observed with administration of benzodiazepines in pharmacologically equivalent dosages; therefore, a distinction between these two drug classes on the basis of withdrawal effects on the sleep electroencephalogram appears unwarranted. Further investigation is required determine why high REM levels are sometimes associated with the withdrawal of sedative-hypnotic agents.